Rod-like Composites Research Articles

Tailored heterogeneous interface based on porous hollow In-Co-C nanorods to construct adjustable multi-band microwave absorber

By rationally controlling the growth of zeolite-imidazolium salt skeleton (ZIF-67) nanoparticles on the hollow indium oxide (In2O3) and the subsequent pyrolysis process, In-Co-C hollow rod-like composites with multiple components were successfully prepared in this work. The synergistic impact of diverse components including In2O3, C, Co3InC0.75, and In not only optimizes impedance matching and improves conductive loss, but also creates significant interfacial polarization. Furthermore, the addition of Co source and pyrolysis temperature was found to have a significant affected on impedance matching and microwave absorption. The optimized In-Co-C sample displayed ultra-broad absorption bandwidth (EAB) of up to 7.12 GHz (10.88–18.0 GHz) at 2.26 mm thickness, which could cover the whole Ku band and part of X-band, outperforming the previously reported MOFs-derived composites. Furthermore, by adjusting the thickness to 2.91 mm and 4.01 mm, the EAB could cover the entire X band and most of the C band. The attenuation mechanisms were systematically investigated through the delta function method and ANSYS high-frequency structure simulator. These findings suggest that the MOFs-derived In-Co-C hollow nanorods could serve as high-performance microwave absorbers with ultra-broad absorption.

High sensitivity and selectivity of formaldehyde sensor based on Nd2O3 @In2O3 heterojunction rod-like composites

The rare-earth material Nd2O3, which has abundant oxygen vacancy defects and unique structural property of 4f‐4f electron leap, shows its great potential for chemical sensing applications. However, the difficulty in selecting suitable Nd-precursor complexes has limited the synthesis and further applications of Nd2O3 materials. Herein, we synthesized Nd(OH)3 using a simple solvent method, followed by calcination by mixing it with the precursor MIL-68(In) to generate Nd2O3 surface-modified In2O3 composites. After that, its gas-sensitive performance was investigated. It was observed that the response of 5 wt% Nd2O3 @In2O3 to formaldehyde (100 ppm) is the highest (850.3), which is 25 times higher than that of In2O3. Compared with In2O3, Nd2O3-decorated In2O3 not only exhibited higher sensitivity and better selectivity but also reduced response time. The improved gas-sensing performance could be attributed to the formation of heterojunctions between Nd2O3 and In2O3 as well as the increase of adsorbed oxygen and defective oxygen. This kind of gas sensor based on Nd2O3-decorated In2O3 has more obvious advantages for fast and high-response detection of formaldehyde.

Morphological diversity effect of graphene quantum dot/MIL88A(Fe) composites on dye and pharmaceuticals (tetracycline and doxycycline) removal

Herein, composites with different morphologies (diamond-like, rod-like, and spindle-like) were successfully synthesized using MIL88A (Fe) and graphene quantum dots (GQDs) to remove Acid Blue 92 (AB92), pharmaceuticals (doxycycline, and tetracycline). Despite the similarity in content, chemical structure, and functional groups of the composites, interesting differences were observed in some of their physicochemical properties (BET, RAMAN, TEM, and SEM) and adsorption performance, which was the turning point of this research. Spindle-like GQDMIL88A composite with the adsorption capacity of 617 mg/g indicated the highest adsorption capacity for Acid Blue 92 (AB92) compared to 335 mg/g for rod-like composites and 114 mg/g for diamond-like composites. Also, for doxycycline removal, the spindle-like composite with the adsorption capacity of 796 mg/g, was still in the first rank, compared to 588 mg/g for rod-like and 469 mg/g for diamond-like GQDMIL88A. The tetracycline adsorption capacity for spindle-like, rod-like, and diamond-like GQDMIL88A composites was 672 mg/g, 398 mg/g, and 300 mg/g, respectively. According to the findings of this study, despite the different adsorption capacities of different GQDMIL88A composite morphologies, all three types are well compatible with the Langmuir isotherm and pseudo-second-order kinetics.

Rigidity Percolation in Disordered 3D Rod Systems

In composite materials composed of a soft polymer matrix and rigid, high aspect-ratio particles, the composite undergoes a transition in mechanical strength when the incorporated particle phase surpasses a critical density. This phenomenon, termed rheological percolation, is well known to occur in many polymer-rod and polymer-platelet composites at a critical density that exceeds the conductivity percolation threshold (which occurs when the conducting particles form a large connected component that spans the composite). Contact percolation in rod-like composites has been routinely exploited to engineer thermal or electrical conductivity in otherwise nonconducting polymers, and the characterization of contact percolation is well established. Mechanical or rheological percolation, however, has evaded a complete theoretical explanation and predictive description. A natural hypothesis is that rheological percolation is due to a rigidity phenomenon, whereby a large rigid component of inclusions spans the composite. Here we build an algorithm to detect the rigidity percolation threshold in rod-polymer composites. We model the composites as systems of randomly distributed, soft-core (intersecting at contact) rods and study the emergence of a giant (i.e., spanning) rigid component. Building on our previous results for two-dimensional composites, we develop an approximate algorithm that identifies spanning rigid components through hierarchically identifying and compressing provably rigid motifs---equivalently, decomposing a giant rigid component into rigid assemblies of a hierarchy of successively smaller rigid components. We apply this algorithm to random monodisperse systems that are generated in Monte Carlo simulations to estimate a rigidity percolation threshold (critical density) and explore its dependence on rod aspect ratio. We show that this transition point---like its contact percolation analogue---scales inversely with the excluded volume of a rod. Moreover, this implies that the critical contact number (i.e., the number of contacts per rod at the rigidity percolation threshold) is constant for aspect ratios above some relatively low value and is lower than the prediction from Maxwell's isostatic condition.

Synthesis of MOF-derived Fe7S8/C rod-like composites by controlled proportion of carbon for highly efficient electromagnetic wave absorption

In this study, we firstly used the MOF-derived Fe7S8/C rod-like composites as absorbers and systematically investigated the synergistic effect of Fe7S8 and carbon in electromagnetic wave absorption applications. By controlling the introduced dosage of ferric salt, the proportion of carbon and Fe7S8 in composites could be adjusted, which made a significant effect on the electromagnetic parameters and absorption performance. When the carbon proportion was about 33.9 wt%, the synergistic effect between Fe7S8 and carbon guaranteed the optimized impedance matching and strong dissipation ability, presenting superb absorption performance. The optimal performance reflected in the minimum reflection loss of −68.86 dB at 12.08 GHz with a thickness of 1.67 mm, and the effective bandwidth was up to 4.56 GHz at 1.45 mm. Therefore, this study provides a facile method for preparing the Fe7S8/C absorbers and emphasizes the significance of the ratios between Fe7S8 and carbon on the electromagnetic parameters and absorption performance.

MOF-derived rod-like composites consisting of iron sulfides embedded in nitrogen-rich carbon as high-performance lithium-ion battery anodes

Rod-like porous composites of iron sulfides embedded in nitrogen-rich carbon have been synthesized through a simultaneous carbonization and sulfuration process of the Fe-based metal-organic framework (MIL-88) for the first time. The composites exhibit combined advantages of the porous structure, uniform distribution of iron sulfide nanoparticles and increased conductivity. As an anode material for lithium-ion batteries (LIBs), the composites show a high reversible capacity of 936.3 mAh g−1 after 300 cycles and an exceptional high-rate capability (1128, 1056, 989, 912, 841 mAh g−1 at the current densities of 0.1, 0.2, 0.4, 0.8, and 1.6 A g−1, respectively). The results indicate that the composites could be a promising candidate for anode materials in LIBs.

EDTA-Na 2 -assisted synthesis of rod-like titanate-TiO 2 composite architectures with enhanced visible-light-driven properties

A simple wet chemical method was developed to synthesize visible-light-driven titanate-TiO2 rod-like composites using ethylenediaminetetraacetic disodium salt (EDTA-Na2) as both template-directed modifier and nitrogen doping source. The synthesized heterojunctions exhibited both enhanced adsorption ability and photocatalytic activity for the degradation of methylene blue (MB) dye under visible light irradiation. EDTA-Na2 was found to alter the condensation pathway of the titanium precursor. This study also identified the different loading effects of EDTA-Na2 on the adsorption and photocatalytic degradation. O2− was the dominant radical for MB photodegradation.

The hybridization of Ag2CO3 rods with g-C3N4 sheets with improved photocatalytic activity

A series of graphitic carbon nitride/silver carbonate (g-C3N4/Ag2CO3) rod-like composites with different weight contents of g-C3N4 have been prepared by a facile precipitation method. The g-C3N4/Ag2CO3 rod-like composites exhibited higher photocatalytic activity than pure Ag2CO3 toward degradation of rhodamine B (RhB) and methylene blue (MB) under visible-light irradiation. The photocatalytic reaction follows a pseudo-first-order reaction and the rate constants for the degradation of RhB and MB by 3.5% g-C3N4/Ag2CO3 are about 2 times and 1.7 times that of pure Ag2CO3, respectively. A possible photocatalytic mechanism was proposed based on the photoluminescence (PL) spectra and a series of radical trapping experimental analyses. The remarkably improved photocatalytic performance should be ascribed to the heterostructure between Ag2CO3 and g-C3N4, which greatly promoted the photoinduced charge transfer and inhibited the recombination of electrons and holes.

Synthesis, Characterization and Anticorrosion Performances Study of Different Acid Doping Polyaniline

Different polyaniline micro/nanostructures were prepared in by oxidative polymerization doped with different acids like citric acid (C6H8O7), H3PO4 and HCl. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and UV–Visible spectral techniques. The rod-like composites, microspheres and nanofiber of polyaniline could be synthesized by different doting. The corrosion studies were carried out on steel plates coated with epoxy coatings containing polyaniline prepared with acid doping and no acid doing. Corrosion protection of these epoxy coatings containing prepared polyaniline (PANI) on steel was studied by Tafel polarization test in 3.5wt% sodium chloride (NaCl) aqueous solution. The results indicated that coatings prepared from acid doped polyaniline particles were found to exhibit excellent corrosion resistance much superior to no acid doped PANI in aggressive environments, and the epoxy coating containing PANI obtained in HCl doping had the best performance of the corrosion protection in all systems under investigation. The possible protective mechanism of PANI was discussed.